Stars, supernovae, black holes and stellar remnants

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Two Telescopes Investigate the Oldest Black Hole Ever Discovered
by Doris Elin Urrutia
November 7, 2023

Conclusion:

(Inverse) In 2017, Yale University astrophysicist Priyamvada Natarajan, who is a co-author of the new study describing the findings, proposed a theoretical model. In it, supermassive black holes in the early universe form when a huge cloud of gas collapses, resulting in what Natarajan calls an “Outsize Black Hole.”

We think that this is the first detection of an ‘Outsize Black Hole’ and the best evidence yet obtained that some black holes form from massive clouds of gas,” Natarajan said in NASA’s statement. “For the first time we are seeing a brief stage where a supermassive black hole weighs about as much as the stars in its galaxy.”

A paper with a deeper investigation into this galaxy and the Outsize Black Hole premise is forthcoming, according to NASA. But the new revelation from Chandra and JWST show that the science of the ancient universe is coming into reach.

Read more here: https://www.inverse.com/science/ancie ... discovery

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Five new pulsars discovered with FAST
https://phys.org/news/2023-11-pulsars-fast.html
by Tomasz Nowakowski , Phys.org

Using the Five-hundred Aperture Spherical Telescope (FAST), astronomers from China and Australia have discovered five new pulsars, two of which turned out to have ultra-short spin periods. The finding was reported in a research paper published November 1 on the preprint server arXiv.

Pulsars are highly magnetized, rotating neutron stars emitting a beam of electromagnetic radiation from their magnetic poles. This radiation can only be observed when the beam of emission is pointing toward the Earth.

The most rapidly rotating pulsars, with rotation periods below 30 milliseconds, are known as millisecond pulsars (MSPs). It is assumed that they are formed in binary systems when the initially more massive component turns into a neutron star that is then spun up due to accretion of matter from the secondary star.

Now, a team of astronomers led by Qi-Jun Zhi of the Guizhou Normal University in Guiyang, China, reports the detection of five new pulsars with FAST as part of a pilot survey at intermediate Galactic latitudes.

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TESS detects new cataclysmic variable system of a rare type

https://phys.org/news/2023-11-tess-cata ... -rare.html

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Please note that while the first citation (see below) is highly technical, the second citation is somewhat more accessible in understanding from a layman’s perspective.

Physicists Simulate a Black Hole in The Lab.

Abstract:

(Physical Review Research) Synthetic horizons in models for quantum matter provide an alternative route to explore fundamental questions of modern gravitational theory. Here we apply these concepts to the problem of emergence of thermal quantum states in the presence of a horizon, by studying ground-state thermalization due to instantaneous horizon creation in a gravitational setting and its condensed matter analog. By a sudden quench to position-dependent hopping amplitudes in a one-dimensional lattice model, we establish the emergence of a thermal state accompanying the formation of a synthetic horizon. The resulting temperature for long chains is shown to be identical to the corresponding Unruh temperature, provided that the postquench Hamiltonian matches the entanglement Hamiltonian of the prequench system. Based on detailed analysis of the outgoing radiation we formulate the conditions required for the synthetic horizon to behave as a purely thermal source, paving a way to explore this interplay of quantum-mechanical and gravitational aspects experimentally.

Source: https://journals.aps.org/prresearch/ab ... .043084


To unpack and help explain what that means:

(Science Alert) Using a chain of atoms in single-file to simulate the event horizon of a black hole, a team of physicists in 2022 observed the equivalent of what we call Hawking radiation – particles born from disturbances in the quantum fluctuations caused by the black hole's break in spacetime.

This, they say, could help resolve the tension between two currently irreconcilable frameworks for describing the Universe: the general theory of relativity, which describes the behavior of gravity as a continuous field known as spacetime; and quantum mechanics, which describes the behavior of discrete particles using the mathematics of probability.

A one-dimensional chain of atoms served as a path for electrons to 'hop' from one position to another. By tuning the ease with which this hopping can occur, the physicists could cause certain properties to vanish, effectively creating a kind of event horizon that interfered with the wave-like nature of the electrons.

The effect of this fake event horizon produced a rise in temperature that matched theoretical expectations of an equivalent black hole system, the team said, but only when part of the chain extended beyond the event horizon.

This could mean the entanglement of particles that straddle the event horizon is instrumental in generating Hawking radiation.

Read more here: https://www.sciencealert.com/physicists ... -glow

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Astronomers Find a Brilliant Explosion That Just Keeps Exploding
by Monica Young
November 21, 2023

Introduction:

(Sky & Telescope) On September 7, 2022, an automatic telescope picked up a blazing dot of blue light some 1,000 times brighter than a typical supernova. The brilliant blue flare lasted only days before it faded away, but not before an automated system had put astronomers on alert.

The system designated the event AT2022tsd, but it some came to be called the “Tasmanian Devil.” It joined the short list of a special class of objects discovered in 2018 known as luminous fast blue optical transients (LFBOTs). Astronomers think these explosive flares are a special kind of supernova, but they could also be stars ripped apart in the intense gravitational field surrounding a neutron star or black hole. The devil, as they say, is in the details.

But while the Tasmanian Devil’s discovery was a welcome surprise, the real bombshell came 100 days later. In December that year, Anna Ho (Cornell University) and colleagues were reviewing routine images that had monitored the fading flare when, to their bewilderment, they found a red-colored burst almost as bright as the original blue one, and in the same position on the sky.

Scouring for more data, both in the archive and then with new observations, the astronomers found another outburst — and then another, and another. The energy of each one of these outbursts is equivalent to that released from an exploding star. Overall, at least 14 flares followed the first one, Ho and colleagues report in Nature, and it’s likely there were many more they missed.

“An event like this has never been witnessed before,” says team member Jeff Cooke (Swinburne University of Technology and the ARC Centre of Excellence in Gravitational Wave Discovery, Australia).

Read more here: https://skyandtelescope.org/astronomy ... xploding/

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12-billion-year-old body of water discovered floating in space

https://www.indy100.com/science-tech/gi ... g-in-space

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Further evidence for quark-matter cores in massive neutron stars
https://phys.org/news/2023-12-evidence- ... utron.html
by Johanna Pellinen, University of Helsinki

Neutron-star cores contain matter at the highest densities reached in our present-day universe, with as much as two solar masses of matter compressed inside a sphere of 25 km in diameter. These astrophysical objects can indeed be thought of as giant atomic nuclei, with gravity compressing their cores to densities exceeding those of individual protons and neutrons many-fold.

These densities make neutron stars interesting astrophysical objects from the point of view of particle and nuclear physics. A longstanding open problem is whether the immense central pressure of neutron stars can compress protons and neutrons into a new phase of matter, known as cold quark matter. In this exotic state of matter, individual protons and neutrons no longer exist.

"Their constituent quarks and gluons are instead liberated from their typical color confinement and are allowed to move almost freely," explains Aleksi Vuorinen, professor of theoretical particle physics at the University of Helsinki.

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In a Huge First, Scientists Have Observed the 'Missing Link' Between Stars and Black Holes
by Michelle Starr
January11, 2024

Introduction:

(Science Alert) In a magnificent first, we finally have direct observational evidence of the stellar process that produces neutron stars and black holes.

From a supernova that exploded in a nearby galaxy, astronomers observed the emergence of something with the hallmarks of such compact objects. It's not clear which kind, neutron star or black hole, but the finding finally confirms that the core collapse of massive stars produces the densest objects in the Universe, in a spectacular explosion of stellar material.

Stellar-mass black holes and neutron stars are thought to be the result of similar processes.

Towards the end of its lifespan, a star runs out of the fuel required to sustain fusion, the process that keeps it burning. There's a somewhat complicated series of events, but ultimately, the star will eject its outer material; the core, no longer supported by the outward pressure of fusion, collapses under gravity to become a super-dense object (for most stars, anyway).

The nature of that object depends on its mass. Stars smaller than eight Suns produce a white dwarf, the eventual predicted fate of the Sun itself.

Read more here: https://www.sciencealert.com/in-a-huge ... k-holes